During manufacture of semiconductors and semiconductor microcircuits, it is frequently necessary to coat the materials from which the semiconductors and microcircuits are manufactured with a polymeric organic substance, generally referred to as a photoresist, e.g., a substance which forms an etch resist upon exposure to light. These photoresists are used to protect selected areas of the surface of the substrate, e.g. silicon, SiO.sub.2 or aluminum, from the action of the etching solution, while such etchant selectively attacks the unprotected area of the substrate. Following completion of the etching operation and washing away of the residual etchant, it is necessary that the resist be removed from the protective surface to permit essential finishing operations.
A common method used in removing the photoresist from the substrate is by contacting the substract with an organic stripper. Heretofore these organic strippers have been composed of various components whose purpose it was to lift and remove the polymeric photoresist from the substrate. However, these stripping solutions have heretofore usually contained phenol or phenol compounds and chlorinated hydrocarbon compounds. The use of phenol or phenol compounds or chlorinated hydrocarbon compounds results in a distinct disadvantage due to the toxicity of phenol as well as the pollution problems arising from the disposal of phenol or phenol compounds such as cresols, phenol sulfonic acid and the like or the disposal of chlorinated hydrocarbon compounds.
Phenol-free and chlorinated hydrocarbon-free strippers are described in U.S. Pat. No. 4,070,203 (issued Jan. 24, 1978 to Neisius et al.). These strippers, having only an alkylbenzenesulfonic acid component of 12-20 carbons and a chlorine-free, aromatic hydrocarbon component with a boiling point above 150.degree. C., suffer from the disadvantage that they cannot be easily rinsed off the inorganic substrate after stripping with aqueous rinsing materials such as deionized water. Instead organic solvents are required to avoid either the polymer or the aromatic solvent precipitating or forming oil beads, respectively, or, if water is used, copious amounts are required. The formation of oil beads is called "oiling out" and may lead to an undesirable oily layer remaining on the inorganic substrate.
It is an object of this invention to provide an effective photoresist stripping solution which is essentially free of phenol, phenol compounds and chlorinated hydrocarbon compounds.
It is an additional object of this invention to provide such a solution which is substantially clean water rinsable such that the hydrocarbon solvent does not oil out and the polymer does not reprecipitate during rinsing.
It is an additional object of this invention to provide a method for removing photoresist polymeric coatings from inorganic substrates with such a stripping solution free from phenol, phenol compounds and chlorinated hydrocarbon compounds which can then be rinsed with an aqueous rinsing agent such as deionized water.
These and other objects will become apparent from the description which follows.